Zhuo, Peng
(2020)
3D printing technology of continuous fibre reinforced polymeric composites for key load carrying structural parts and components.
PhD thesis, University of Nottingham.
Abstract
In recent years, 3DP technology has developed to include composite materials. Most of the development to date in this area has involved particulate or short fibre reinforced composites, whilst continuous fibre printing remains a relatively novel research area. By employing continuous fibre as a reinforcement for the composite, the mechanical properties of the printed part can be improved greatly. More importantly, fibre steering can be achieved by the new technology, which brings new possibilities and challenges to composite materials and structures.
Firstly, the state-of-the-art of CF-3DP technology of FDM or FFF process is reviewed. The materials and devices being used in the literature, and the different processing methods are discussed in detail. Despite improvements compared to 3D printed pure plastics, the mechanical performance of current CF-3DP composites are not yet in a position to compete with conventionally processed composites due to defects and low fibre volume fraction.
In order to realize CF-3DP and achieve fibre steering, an open-source plastic FDM printer was adapted, and a commingled fibre tow was utilized as the feedstock material. A pultrusion process was developed to manufacture the feedstock for the CF-3DP technology. The printing process parameters were investigated, and the quality of the CF-3DP composites was examined. Coupon test specimens were produced, and static mechanical tests were performed. The test results showed excellent longitudinal tensile properties while the matrix sensitive properties were expected to be low as a generic weakness of UD composites in general and the type of matrix material involved. Although the mechanical properties may not be comparable with composites materials manufactured by conventional methods, they are superior to those manufactured by the commercial printer and those in most of the literature.
A novel design philosophy for a composite lug structure was proposed, as an example of a strength controlled key load carrying part widely employed, in particular, in aerospace structures. In the proposed design, fibres were tailored around the hole region to avoid fibre cutting. Several layer patterns with curvilinear fibre paths were designed considering the given load cases. Lug samples were manufactured using the CF-3DP technology to demonstrate its capability of overcoming the limitations of conventional composite manufacturing processes. Tensile and compressive tests were performed on the lug samples with proposed steered fibre patterns to demonstrate the proposed design philosophy. The results showed that the lug samples with curvilinear fibre showed different behaviour compared to the conventional quasi-isotropic layup samples. A preliminary FE model was created to evaluate the lug structure.
In this study, a laboratory level continuous fibre 3D printing device and a feedstock material manufacturing device were developed. Fibre volume fraction of the printed composites reached over 45%, which was 15% higher than that manufactured by the commercial printer. Coupon level mechanical tests on the printed composites were performed, in which not only 0 tensile but a wider range of tests were carried out. Overall, the mechanical performance was poor compared to that of conventional composites, due to low fibre volume fraction and poor fibre wetting. Fibre steering was achieved using the modified printer, which was able to realize the proposed fibre path design. Lug samples with curvilinear fibre patterns were manufactured and tested, which was original in this area. However, challenges still remain in materials and process development. New design, modelling and analysis methods are needed before these novel composite structures can find their practical applications.
Actions (Archive Staff Only)
 |
Edit View |
Tools
Tools
